﻿/*
** 2001 September 15
**
** The author disclaims copyright to this source code.  In place of
** a legal notice, here is a blessing:
**
**    May you do good and not evil.
**    May you find forgiveness for yourself and forgive others.
**    May you share freely, never taking more than you give.
**
*************************************************************************
** This module contains C code that generates VDBE code used to process
** the WHERE clause of SQL statements.  This module is reponsible for
** generating the code that loops through a table looking for applicable
** rows.  Indices are selected and used to speed the search when doing
** so is applicable.  Because this module is responsible for selecting
** indices, you might also think of this module as the "query optimizer".
**
** $Id: where.c,v 1.206 2006/03/28 23:55:58 drh Exp $
*/
#include "sqliteInt.h"

/*
** The number of bits in a Bitmask.  "BMS" means "BitMask Size".
*/
#define BMS  (sizeof(Bitmask)*8)

/*
** Determine the number of elements in an array.
*/
#define ARRAYSIZE(X)  (sizeof(X)/sizeof(X[0]))

/*
** Trace output macros
*/
#if defined(SQLITE_TEST) || defined(SQLITE_DEBUG)
int sqlite3_where_trace = 0;
# define TRACE(X)  if(sqlite3_where_trace) sqlite3DebugPrintf X
#else
# define TRACE(X)
#endif

/* Forward reference
*/
typedef struct WhereClause WhereClause;

/*
** The query generator uses an array of instances of this structure to
** help it analyze the subexpressions of the WHERE clause.  Each WHERE
** clause subexpression is separated from the others by an AND operator.
**
** All WhereTerms are collected into a single WhereClause structure.
** The following identity holds:
**
**        WhereTerm.pWC->a[WhereTerm.idx] == WhereTerm
**
** When a term is of the form:
**
**              X <op> <expr>
**
** where X is a column name and <op> is one of certain operators,
** then WhereTerm.leftCursor and WhereTerm.leftColumn record the
** cursor number and column number for X.  WhereTerm.operator records
** the <op> using a bitmask encoding defined by WO_xxx below.  The
** use of a bitmask encoding for the operator allows us to search
** quickly for terms that match any of several different operators.
**
** prereqRight and prereqAll record sets of cursor numbers,
** but they do so indirectly.  A single ExprMaskSet structure translates
** cursor number into bits and the translated bit is stored in the prereq
** fields.  The translation is used in order to maximize the number of
** bits that will fit in a Bitmask.  The VDBE cursor numbers might be
** spread out over the non-negative integers.  For example, the cursor
** numbers might be 3, 8, 9, 10, 20, 23, 41, and 45.  The ExprMaskSet
** translates these sparse cursor numbers into consecutive integers
** beginning with 0 in order to make the best possible use of the available
** bits in the Bitmask.  So, in the example above, the cursor numbers
** would be mapped into integers 0 through 7.
*/
typedef struct WhereTerm WhereTerm;
struct WhereTerm {
  Expr *pExpr;            /* Pointer to the subexpression */
  i16 iParent;            /* Disable pWC->a[iParent] when this term disabled */
  i16 leftCursor;         /* Cursor number of X in "X <op> <expr>" */
  i16 leftColumn;         /* Column number of X in "X <op> <expr>" */
  u16 eOperator;          /* A WO_xx value describing <op> */
  u8 flags;               /* Bit flags.  See below */
  u8 nChild;              /* Number of children that must disable us */
  WhereClause *pWC;       /* The clause this term is part of */
  Bitmask prereqRight;    /* Bitmask of tables used by pRight */
  Bitmask prereqAll;      /* Bitmask of tables referenced by p */
};

/*
** Allowed values of WhereTerm.flags
*/
#define TERM_DYNAMIC    0x01   /* Need to call sqlite3ExprDelete(pExpr) */
#define TERM_VIRTUAL    0x02   /* Added by the optimizer.  Do not code */
#define TERM_CODED      0x04   /* This term is already coded */
#define TERM_COPIED     0x08   /* Has a child */
#define TERM_OR_OK      0x10   /* Used during OR-clause processing */

/*
** An instance of the following structure holds all information about a
** WHERE clause.  Mostly this is a container for one or more WhereTerms.
*/
struct WhereClause {
  Parse *pParse;           /* The parser context */
  int nTerm;               /* Number of terms */
  int nSlot;               /* Number of entries in a[] */
  WhereTerm *a;            /* Each a[] describes a term of the WHERE cluase */
  WhereTerm aStatic[10];   /* Initial static space for a[] */
};

/*
** An instance of the following structure keeps track of a mapping
** between VDBE cursor numbers and bits of the bitmasks in WhereTerm.
**
** The VDBE cursor numbers are small integers contained in
** SrcList_item.iCursor and Expr.iTable fields.  For any given WHERE
** clause, the cursor numbers might not begin with 0 and they might
** contain gaps in the numbering sequence.  But we want to make maximum
** use of the bits in our bitmasks.  This structure provides a mapping
** from the sparse cursor numbers into consecutive integers beginning
** with 0.
**
** If ExprMaskSet.ix[A]==B it means that The A-th bit of a Bitmask
** corresponds VDBE cursor number B.  The A-th bit of a bitmask is 1<<A.
**
** For example, if the WHERE clause expression used these VDBE
** cursors:  4, 5, 8, 29, 57, 73.  Then the  ExprMaskSet structure
** would map those cursor numbers into bits 0 through 5.
**
** Note that the mapping is not necessarily ordered.  In the example
** above, the mapping might go like this:  4->3, 5->1, 8->2, 29->0,
** 57->5, 73->4.  Or one of 719 other combinations might be used. It
** does not really matter.  What is important is that sparse cursor
** numbers all get mapped into bit numbers that begin with 0 and contain
** no gaps.
*/
typedef struct ExprMaskSet ExprMaskSet;
struct ExprMaskSet {
  int n;                        /* Number of assigned cursor values */
  int ix[sizeof(Bitmask)*8];    /* Cursor assigned to each bit */
};


/*
** Bitmasks for the operators that indices are able to exploit.  An
** OR-ed combination of these values can be used when searching for
** terms in the where clause.
*/
#define WO_IN     1
#define WO_EQ     2
#define WO_LT     (WO_EQ<<(TK_LT-TK_EQ))
#define WO_LE     (WO_EQ<<(TK_LE-TK_EQ))
#define WO_GT     (WO_EQ<<(TK_GT-TK_EQ))
#define WO_GE     (WO_EQ<<(TK_GE-TK_EQ))

/*
** Value for flags returned by bestIndex()
*/
#define WHERE_ROWID_EQ       0x0001   /* rowid=EXPR or rowid IN (...) */
#define WHERE_ROWID_RANGE    0x0002   /* rowid<EXPR and/or rowid>EXPR */
#define WHERE_COLUMN_EQ      0x0010   /* x=EXPR or x IN (...) */
#define WHERE_COLUMN_RANGE   0x0020   /* x<EXPR and/or x>EXPR */
#define WHERE_COLUMN_IN      0x0040   /* x IN (...) */
#define WHERE_TOP_LIMIT      0x0100   /* x<EXPR or x<=EXPR constraint */
#define WHERE_BTM_LIMIT      0x0200   /* x>EXPR or x>=EXPR constraint */
#define WHERE_IDX_ONLY       0x0800   /* Use index only - omit table */
#define WHERE_ORDERBY        0x1000   /* Output will appear in correct order */
#define WHERE_REVERSE        0x2000   /* Scan in reverse order */
#define WHERE_UNIQUE         0x4000   /* Selects no more than one row */

/*
** Initialize a preallocated WhereClause structure.
*/
static void whereClauseInit(WhereClause *pWC, Parse *pParse){
  pWC->pParse = pParse;
  pWC->nTerm = 0;
  pWC->nSlot = ARRAYSIZE(pWC->aStatic);
  pWC->a = pWC->aStatic;
}

/*
** Deallocate a WhereClause structure.  The WhereClause structure
** itself is not freed.  This routine is the inverse of whereClauseInit().
*/
static void whereClauseClear(WhereClause *pWC){
  int i;
  WhereTerm *a;
  for(i=pWC->nTerm-1, a=pWC->a; i>=0; i--, a++){
    if( a->flags & TERM_DYNAMIC ){
      sqlite3ExprDelete(a->pExpr);
    }
  }
  if( pWC->a!=pWC->aStatic ){
    sqliteFree(pWC->a);
  }
}

/*
** Add a new entries to the WhereClause structure.  Increase the allocated
** space as necessary.
**
** WARNING:  This routine might reallocate the space used to store
** WhereTerms.  All pointers to WhereTerms should be invalided after
** calling this routine.  Such pointers may be reinitialized by referencing
** the pWC->a[] array.
*/
static int whereClauseInsert(WhereClause *pWC, Expr *p, int flags){
  WhereTerm *pTerm;
  int idx;
  if( pWC->nTerm>=pWC->nSlot ){
    WhereTerm *pOld = pWC->a;
    pWC->a = sqliteMalloc( sizeof(pWC->a[0])*pWC->nSlot*2 );
    if( pWC->a==0 ) return 0;
    memcpy(pWC->a, pOld, sizeof(pWC->a[0])*pWC->nTerm);
    if( pOld!=pWC->aStatic ){
      sqliteFree(pOld);
    }
    pWC->nSlot *= 2;
  }
  pTerm = &pWC->a[idx = pWC->nTerm];
  pWC->nTerm++;
  pTerm->pExpr = p;
  pTerm->flags = flags;
  pTerm->pWC = pWC;
  pTerm->iParent = -1;
  return idx;
}

/*
** This routine identifies subexpressions in the WHERE clause where
** each subexpression is separated by the AND operator or some other
** operator specified in the op parameter.  The WhereClause structure
** is filled with pointers to subexpressions.  For example:
**
**    WHERE  a=='hello' AND coalesce(b,11)<10 AND (c+12!=d OR c==22)
**           \________/     \_______________/     \________________/
**            slot[0]            slot[1]               slot[2]
**
** The original WHERE clause in pExpr is unaltered.  All this routine
** does is make slot[] entries point to substructure within pExpr.
**
** In the previous sentence and in the diagram, "slot[]" refers to
** the WhereClause.a[] array.  This array grows as needed to contain
** all terms of the WHERE clause.
*/
static void whereSplit(WhereClause *pWC, Expr *pExpr, int op){
  if( pExpr==0 ) return;
  if( pExpr->op!=op ){
    whereClauseInsert(pWC, pExpr, 0);
  }else{
    whereSplit(pWC, pExpr->pLeft, op);
    whereSplit(pWC, pExpr->pRight, op);
  }
}

/*
** Initialize an expression mask set
*/
#define initMaskSet(P)  memset(P, 0, sizeof(*P))

/*
** Return the bitmask for the given cursor number.  Return 0 if
** iCursor is not in the set.
*/
static Bitmask getMask(ExprMaskSet *pMaskSet, int iCursor){
  int i;
  for(i=0; i<pMaskSet->n; i++){
    if( pMaskSet->ix[i]==iCursor ){
      return ((Bitmask)1)<<i;
    }
  }
  return 0;
}

/*
** Create a new mask for cursor iCursor.
**
** There is one cursor per table in the FROM clause.  The number of
** tables in the FROM clause is limited by a test early in the
** sqlite3WhereBegin() routine.  So we know that the pMaskSet->ix[]
** array will never overflow.
*/
static void createMask(ExprMaskSet *pMaskSet, int iCursor){
  assert( pMaskSet->n < ARRAYSIZE(pMaskSet->ix) );
  pMaskSet->ix[pMaskSet->n++] = iCursor;
}

/*
** This routine walks (recursively) an expression tree and generates
** a bitmask indicating which tables are used in that expression
** tree.
**
** In order for this routine to work, the calling function must have
** previously invoked sqlite3ExprResolveNames() on the expression.  See
** the header comment on that routine for additional information.
** The sqlite3ExprResolveNames() routines looks for column names and
** sets their opcodes to TK_COLUMN and their Expr.iTable fields to
** the VDBE cursor number of the table.  This routine just has to
** translate the cursor numbers into bitmask values and OR all
** the bitmasks together.
*/
static Bitmask exprListTableUsage(ExprMaskSet*, ExprList*);
static Bitmask exprSelectTableUsage(ExprMaskSet*, Select*);
static Bitmask exprTableUsage(ExprMaskSet *pMaskSet, Expr *p){
  Bitmask mask = 0;
  if( p==0 ) return 0;
  if( p->op==TK_COLUMN ){
    mask = getMask(pMaskSet, p->iTable);
    return mask;
  }
  mask = exprTableUsage(pMaskSet, p->pRight);
  mask |= exprTableUsage(pMaskSet, p->pLeft);
  mask |= exprListTableUsage(pMaskSet, p->pList);
  mask |= exprSelectTableUsage(pMaskSet, p->pSelect);
  return mask;
}
static Bitmask exprListTableUsage(ExprMaskSet *pMaskSet, ExprList *pList){
  int i;
  Bitmask mask = 0;
  if( pList ){
    for(i=0; i<pList->nExpr; i++){
      mask |= exprTableUsage(pMaskSet, pList->a[i].pExpr);
    }
  }
  return mask;
}
static Bitmask exprSelectTableUsage(ExprMaskSet *pMaskSet, Select *pS){
  Bitmask mask;
  if( pS==0 ){
    mask = 0;
  }else{
    mask = exprListTableUsage(pMaskSet, pS->pEList);
    mask |= exprListTableUsage(pMaskSet, pS->pGroupBy);
    mask |= exprListTableUsage(pMaskSet, pS->pOrderBy);
    mask |= exprTableUsage(pMaskSet, pS->pWhere);
    mask |= exprTableUsage(pMaskSet, pS->pHaving);
  }
  return mask;
}

/*
** Return TRUE if the given operator is one of the operators that is
** allowed for an indexable WHERE clause term.  The allowed operators are
** "=", "<", ">", "<=", ">=", and "IN".
*/
static int allowedOp(int op){
  assert( TK_GT>TK_EQ && TK_GT<TK_GE );
  assert( TK_LT>TK_EQ && TK_LT<TK_GE );
  assert( TK_LE>TK_EQ && TK_LE<TK_GE );
  assert( TK_GE==TK_EQ+4 );
  return op==TK_IN || (op>=TK_EQ && op<=TK_GE);
}

/*
** Swap two objects of type T.
*/
#define SWAP(TYPE,A,B) {TYPE t=A; A=B; B=t;}

/*
** Commute a comparision operator.  Expressions of the form "X op Y"
** are converted into "Y op X".
*/
static void exprCommute(Expr *pExpr){
  assert( allowedOp(pExpr->op) && pExpr->op!=TK_IN );
  SWAP(CollSeq*,pExpr->pRight->pColl,pExpr->pLeft->pColl);
  SWAP(Expr*,pExpr->pRight,pExpr->pLeft);
  if( pExpr->op>=TK_GT ){
    assert( TK_LT==TK_GT+2 );
    assert( TK_GE==TK_LE+2 );
    assert( TK_GT>TK_EQ );
    assert( TK_GT<TK_LE );
    assert( pExpr->op>=TK_GT && pExpr->op<=TK_GE );
    pExpr->op = ((pExpr->op-TK_GT)^2)+TK_GT;
  }
}

/*
** Translate from TK_xx operator to WO_xx bitmask.
*/
static int operatorMask(int op){
  int c;
  assert( allowedOp(op) );
  if( op==TK_IN ){
    c = WO_IN;
  }else{
    c = WO_EQ<<(op-TK_EQ);
  }
  assert( op!=TK_IN || c==WO_IN );
  assert( op!=TK_EQ || c==WO_EQ );
  assert( op!=TK_LT || c==WO_LT );
  assert( op!=TK_LE || c==WO_LE );
  assert( op!=TK_GT || c==WO_GT );
  assert( op!=TK_GE || c==WO_GE );
  return c;
}

/*
** Search for a term in the WHERE clause that is of the form "X <op> <expr>"
** where X is a reference to the iColumn of table iCur and <op> is one of
** the WO_xx operator codes specified by the op parameter.
** Return a pointer to the term.  Return 0 if not found.
*/
/* static WhereTerm *findTerm( */
/*   WhereClause *pWC,     /1* The WHERE clause to be searched *1/ */
/*   int iCur,             /1* Cursor number of LHS *1/ */
/*   int iColumn,          /1* Column number of LHS *1/ */
/*   Bitmask notReady,     /1* RHS must not overlap with this mask *1/ */
/*   u16 op,               /1* Mask of WO_xx values describing operator *1/ */
/*   Index *pIdx           /1* Must be compatible with this index, if not NULL *1/ */
/* ){ */
/*   WhereTerm *pTerm; */
/*   int k; */
/*   for(pTerm=pWC->a, k=pWC->nTerm; k; k--, pTerm++){ */
/*     if( pTerm->leftCursor==iCur */
/*        && (pTerm->prereqRight & notReady)==0 */
/*        && pTerm->leftColumn==iColumn */
/*        && (pTerm->eOperator & op)!=0 */
/*     ){ */
/*       if( iCur>=0 && pIdx ){ */
/*         Expr *pX = pTerm->pExpr; */
/*         CollSeq *pColl; */
/*         char idxaff; */
/*         int j; */
/*         Parse *pParse = pWC->pParse; */

/*         idxaff = pIdx->pTable->aCol[iColumn].affinity; */
/*         if( !sqlite3IndexAffinityOk(pX, idxaff) ) continue; */
/*         pColl = sqlite3ExprCollSeq(pParse, pX->pLeft); */
/*         if( !pColl ){ */
/*           if( pX->pRight ){ */
/*             pColl = sqlite3ExprCollSeq(pParse, pX->pRight); */
/*           } */
/*           if( !pColl ){ */
/*             pColl = pParse->db->pDfltColl; */
/*           } */
/*         } */
/*         for(j=0; j<pIdx->nColumn && pIdx->aiColumn[j]!=iColumn; j++){} */
/*         assert( j<pIdx->nColumn ); */
/*         if( sqlite3StrICmp(pColl->zName, pIdx->azColl[j]) ) continue; */
/*       } */
/*       return pTerm; */
/*     } */
/*   } */
/*   return 0; */
/* } */

/* Forward reference */
static void exprAnalyze(SrcList*, ExprMaskSet*, WhereClause*, int);

/*
** Call exprAnalyze on all terms in a WHERE clause.
**
**
*/
static void exprAnalyzeAll(
  SrcList *pTabList,       /* the FROM clause */
  ExprMaskSet *pMaskSet,   /* table masks */
  WhereClause *pWC         /* the WHERE clause to be analyzed */
){
  int i;
  for(i=pWC->nTerm-1; i>=0; i--){
    exprAnalyze(pTabList, pMaskSet, pWC, i);
  }
}

#ifndef SQLITE_OMIT_LIKE_OPTIMIZATION
/*
** Check to see if the given expression is a LIKE or GLOB operator that
** can be optimized using inequality constraints.  Return TRUE if it is
** so and false if not.
**
** In order for the operator to be optimizible, the RHS must be a string
** literal that does not begin with a wildcard.
*/
/* static int isLikeOrGlob( */
/*   sqlite3 *db,      /1* The database *1/ */
/*   Expr *pExpr,      /1* Test this expression *1/ */
/*   int *pnPattern,   /1* Number of non-wildcard prefix characters *1/ */
/*   int *pisComplete  /1* True if the only wildcard is % in the last character *1/ */
/* ){ */
/*   const char *z; */
/*   Expr *pRight, *pLeft; */
/*   ExprList *pList; */
/*   int c, cnt; */
/*   int noCase; */
/*   char wc[3]; */
/*   CollSeq *pColl; */

/*   if( !sqlite3IsLikeFunction(db, pExpr, &noCase, wc) ){ */
/*     return 0; */
/*   } */
/*   pList = pExpr->pList; */
/*   pRight = pList->a[0].pExpr; */
/*   if( pRight->op!=TK_STRING ){ */
/*     return 0; */
/*   } */
/*   pLeft = pList->a[1].pExpr; */
/*   if( pLeft->op!=TK_COLUMN ){ */
/*     return 0; */
/*   } */
/*   pColl = pLeft->pColl; */
/*   if( pColl==0 ){ */
/*     pColl = db->pDfltColl; */
/*   } */
/*   if( (pColl->type!=SQLITE_COLL_BINARY || noCase) && */
/*       (pColl->type!=SQLITE_COLL_NOCASE || !noCase) ){ */
/*     return 0; */
/*   } */
/*   sqlite3DequoteExpr(pRight); */
/*   z = (char *)pRight->token.z; */
/*   for(cnt=0; (c=z[cnt])!=0 && c!=wc[0] && c!=wc[1] && c!=wc[2]; cnt++){} */
/*   if( cnt==0 || 255==(u8)z[cnt] ){ */
/*     return 0; */
/*   } */
/*   *pisComplete = z[cnt]==wc[0] && z[cnt+1]==0; */
/*   *pnPattern = cnt; */
/*   return 1; */
/* } */
#endif /* SQLITE_OMIT_LIKE_OPTIMIZATION */

/*
** If the pBase expression originated in the ON or USING clause of
** a join, then transfer the appropriate markings over to derived.
*/
/* static void transferJoinMarkings(Expr *pDerived, Expr *pBase){ */
/*   pDerived->flags |= pBase->flags & EP_FromJoin; */
/*   pDerived->iRightJoinTable = pBase->iRightJoinTable; */
/* } */


/*
** The input to this routine is an WhereTerm structure with only the
** "pExpr" field filled in.  The job of this routine is to analyze the
** subexpression and populate all the other fields of the WhereTerm
** structure.
**
** If the expression is of the form "<expr> <op> X" it gets commuted
** to the standard form of "X <op> <expr>".  If the expression is of
** the form "X <op> Y" where both X and Y are columns, then the original
** expression is unchanged and a new virtual expression of the form
** "Y <op> X" is added to the WHERE clause and analyzed separately.
*/
static void exprAnalyze(
  SrcList *pSrc,            /* the FROM clause */
  ExprMaskSet *pMaskSet,    /* table masks */
  WhereClause *pWC,         /* the WHERE clause */
  int idxTerm               /* Index of the term to be analyzed */
){
  /* WhereTerm *pTerm = &pWC->a[idxTerm]; */
  /* Expr *pExpr = pTerm->pExpr; */
  /* Bitmask prereqLeft; */
  /* Bitmask prereqAll; */
  /* int nPattern; */
  /* int isComplete; */

  /* if( sqlite3MallocFailed() ) return; */
  /* prereqLeft = exprTableUsage(pMaskSet, pExpr->pLeft); */
  /* if( pExpr->op==TK_IN ){ */
  /*   assert( pExpr->pRight==0 ); */
  /*   pTerm->prereqRight = exprListTableUsage(pMaskSet, pExpr->pList) */
  /*                         | exprSelectTableUsage(pMaskSet, pExpr->pSelect); */
  /* }else{ */
  /*   pTerm->prereqRight = exprTableUsage(pMaskSet, pExpr->pRight); */
  /* } */
  /* prereqAll = exprTableUsage(pMaskSet, pExpr); */
  /* if( ExprHasProperty(pExpr, EP_FromJoin) ){ */
  /*   prereqAll |= getMask(pMaskSet, pExpr->iRightJoinTable); */
  /* } */
  /* pTerm->prereqAll = prereqAll; */
  /* pTerm->leftCursor = -1; */
  /* pTerm->iParent = -1; */
  /* pTerm->eOperator = 0; */
  /* if( allowedOp(pExpr->op) && (pTerm->prereqRight & prereqLeft)==0 ){ */
  /*   Expr *pLeft = pExpr->pLeft; */
  /*   Expr *pRight = pExpr->pRight; */
  /*   if( pLeft->op==TK_COLUMN ){ */
  /*     pTerm->leftCursor = pLeft->iTable; */
  /*     pTerm->leftColumn = pLeft->iColumn; */
  /*     pTerm->eOperator = operatorMask(pExpr->op); */
  /*   } */
  /*   if( pRight && pRight->op==TK_COLUMN ){ */
  /*     WhereTerm *pNew; */
  /*     Expr *pDup; */
  /*     if( pTerm->leftCursor>=0 ){ */
  /*       int idxNew; */
  /*       pDup = sqlite3ExprDup(pExpr); */
  /*       idxNew = whereClauseInsert(pWC, pDup, TERM_VIRTUAL|TERM_DYNAMIC); */
  /*       if( idxNew==0 ) return; */
  /*       pNew = &pWC->a[idxNew]; */
  /*       pNew->iParent = idxTerm; */
  /*       pTerm = &pWC->a[idxTerm]; */
  /*       pTerm->nChild = 1; */
  /*       pTerm->flags |= TERM_COPIED; */
  /*     }else{ */
  /*       pDup = pExpr; */
  /*       pNew = pTerm; */
  /*     } */
  /*     exprCommute(pDup); */
  /*     pLeft = pDup->pLeft; */
  /*     pNew->leftCursor = pLeft->iTable; */
  /*     pNew->leftColumn = pLeft->iColumn; */
  /*     pNew->prereqRight = prereqLeft; */
  /*     pNew->prereqAll = prereqAll; */
  /*     pNew->eOperator = operatorMask(pDup->op); */
  /*   } */
  /* } */

/* #ifndef SQLITE_OMIT_BETWEEN_OPTIMIZATION */
  /* /1* If a term is the BETWEEN operator, create two new virtual terms */
  /* ** that define the range that the BETWEEN implements. */
  /* *1/ */
  /* else if( pExpr->op==TK_BETWEEN ){ */
  /*   ExprList *pList = pExpr->pList; */
  /*   int i; */
  /*   static const u8 ops[] = {TK_GE, TK_LE}; */
  /*   assert( pList!=0 ); */
  /*   assert( pList->nExpr==2 ); */
  /*   for(i=0; i<2; i++){ */
  /*     Expr *pNewExpr; */
  /*     int idxNew; */
  /*     pNewExpr = sqlite3Expr(ops[i], sqlite3ExprDup(pExpr->pLeft), */
  /*                            sqlite3ExprDup(pList->a[i].pExpr), 0); */
  /*     idxNew = whereClauseInsert(pWC, pNewExpr, TERM_VIRTUAL|TERM_DYNAMIC); */
  /*     exprAnalyze(pSrc, pMaskSet, pWC, idxNew); */
  /*     pTerm = &pWC->a[idxTerm]; */
  /*     pWC->a[idxNew].iParent = idxTerm; */
  /*   } */
  /*   pTerm->nChild = 2; */
  /* } */
/* #endif /1* SQLITE_OMIT_BETWEEN_OPTIMIZATION *1/ */

/* #if !defined(SQLITE_OMIT_OR_OPTIMIZATION) && !defined(SQLITE_OMIT_SUBQUERY) */
  /* /1* Attempt to convert OR-connected terms into an IN operator so that */
  /* ** they can make use of indices.  Example: */
  /* ** */
  /* **      x = expr1  OR  expr2 = x  OR  x = expr3 */
  /* ** */
  /* ** is converted into */
  /* ** */
  /* **      x IN (expr1,expr2,expr3) */
  /* ** */
  /* ** This optimization must be omitted if OMIT_SUBQUERY is defined because */
  /* ** the compiler for the the IN operator is part of sub-queries. */
  /* *1/ */
  /* else if( pExpr->op==TK_OR ){ */
  /*   int ok; */
  /*   int i, j; */
  /*   int iColumn, iCursor; */
  /*   WhereClause sOr; */
  /*   WhereTerm *pOrTerm; */

  /*   assert( (pTerm->flags & TERM_DYNAMIC)==0 ); */
  /*   whereClauseInit(&sOr, pWC->pParse); */
  /*   whereSplit(&sOr, pExpr, TK_OR); */
  /*   exprAnalyzeAll(pSrc, pMaskSet, &sOr); */
  /*   assert( sOr.nTerm>0 ); */
  /*   j = 0; */
  /*   do{ */
  /*     iColumn = sOr.a[j].leftColumn; */
  /*     iCursor = sOr.a[j].leftCursor; */
  /*     ok = iCursor>=0; */
  /*     for(i=sOr.nTerm-1, pOrTerm=sOr.a; i>=0 && ok; i--, pOrTerm++){ */
  /*       if( pOrTerm->eOperator!=WO_EQ ){ */
  /*         goto or_not_possible; */
  /*       } */
  /*       if( pOrTerm->leftCursor==iCursor && pOrTerm->leftColumn==iColumn ){ */
  /*         pOrTerm->flags |= TERM_OR_OK; */
  /*       }else if( (pOrTerm->flags & TERM_COPIED)!=0 || */
  /*                   ((pOrTerm->flags & TERM_VIRTUAL)!=0 && */
  /*                    (sOr.a[pOrTerm->iParent].flags & TERM_OR_OK)!=0) ){ */
  /*         pOrTerm->flags &= ~TERM_OR_OK; */
  /*       }else{ */
  /*         ok = 0; */
  /*       } */
  /*     } */
  /*   }while( !ok && (sOr.a[j++].flags & TERM_COPIED)!=0 && j<sOr.nTerm ); */
  /*   if( ok ){ */
  /*     ExprList *pList = 0; */
  /*     Expr *pNew, *pDup; */
  /*     for(i=sOr.nTerm-1, pOrTerm=sOr.a; i>=0 && ok; i--, pOrTerm++){ */
  /*       if( (pOrTerm->flags & TERM_OR_OK)==0 ) continue; */
  /*       pDup = sqlite3ExprDup(pOrTerm->pExpr->pRight); */
  /*       pList = sqlite3ExprListAppend(pList, pDup, 0); */
  /*     } */
  /*     pDup = sqlite3Expr(TK_COLUMN, 0, 0, 0); */
  /*     if( pDup ){ */
  /*       pDup->iTable = iCursor; */
  /*       pDup->iColumn = iColumn; */
  /*     } */
  /*     pNew = sqlite3Expr(TK_IN, pDup, 0, 0); */
  /*     if( pNew ){ */
  /*       int idxNew; */
  /*       transferJoinMarkings(pNew, pExpr); */
  /*       pNew->pList = pList; */
  /*       idxNew = whereClauseInsert(pWC, pNew, TERM_VIRTUAL|TERM_DYNAMIC); */
  /*       exprAnalyze(pSrc, pMaskSet, pWC, idxNew); */
  /*       pTerm = &pWC->a[idxTerm]; */
  /*       pWC->a[idxNew].iParent = idxTerm; */
  /*       pTerm->nChild = 1; */
  /*     }else{ */
  /*       sqlite3ExprListDelete(pList); */
  /*     } */
  /*   } */
/* or_not_possible: */
  /*   whereClauseClear(&sOr); */
  /* } */
/* #endif /1* SQLITE_OMIT_OR_OPTIMIZATION *1/ */

/* #ifndef SQLITE_OMIT_LIKE_OPTIMIZATION */
  /* /1* Add constraints to reduce the search space on a LIKE or GLOB */
  /* ** operator. */
  /* *1/ */
  /* if( isLikeOrGlob(pWC->pParse->db, pExpr, &nPattern, &isComplete) ){ */
  /*   Expr *pLeft, *pRight; */
  /*   Expr *pStr1, *pStr2; */
  /*   Expr *pNewExpr1, *pNewExpr2; */
  /*   int idxNew1, idxNew2; */

  /*   pLeft = pExpr->pList->a[1].pExpr; */
  /*   pRight = pExpr->pList->a[0].pExpr; */
  /*   pStr1 = sqlite3Expr(TK_STRING, 0, 0, 0); */
  /*   if( pStr1 ){ */
  /*     sqlite3TokenCopy(&pStr1->token, &pRight->token); */
  /*     pStr1->token.n = nPattern; */
  /*   } */
  /*   pStr2 = sqlite3ExprDup(pStr1); */
  /*   if( pStr2 ){ */
  /*     assert( pStr2->token.dyn ); */
  /*     ++*(u8*)&pStr2->token.z[nPattern-1]; */
  /*   } */
  /*   pNewExpr1 = sqlite3Expr(TK_GE, sqlite3ExprDup(pLeft), pStr1, 0); */
  /*   idxNew1 = whereClauseInsert(pWC, pNewExpr1, TERM_VIRTUAL|TERM_DYNAMIC); */
  /*   exprAnalyze(pSrc, pMaskSet, pWC, idxNew1); */
  /*   pNewExpr2 = sqlite3Expr(TK_LT, sqlite3ExprDup(pLeft), pStr2, 0); */
  /*   idxNew2 = whereClauseInsert(pWC, pNewExpr2, TERM_VIRTUAL|TERM_DYNAMIC); */
  /*   exprAnalyze(pSrc, pMaskSet, pWC, idxNew2); */
  /*   pTerm = &pWC->a[idxTerm]; */
  /*   if( isComplete ){ */
  /*     pWC->a[idxNew1].iParent = idxTerm; */
  /*     pWC->a[idxNew2].iParent = idxTerm; */
  /*     pTerm->nChild = 2; */
  /*   } */
  /* } */
/* #endif /1* SQLITE_OMIT_LIKE_OPTIMIZATION *1/ */
}


/*
** This routine decides if pIdx can be used to satisfy the ORDER BY
** clause.  If it can, it returns 1.  If pIdx cannot satisfy the
** ORDER BY clause, this routine returns 0.
**
** pOrderBy is an ORDER BY clause from a SELECT statement.  pTab is the
** left-most table in the FROM clause of that same SELECT statement and
** the table has a cursor number of "base".  pIdx is an index on pTab.
**
** nEqCol is the number of columns of pIdx that are used as equality
** constraints.  Any of these columns may be missing from the ORDER BY
** clause and the match can still be a success.
**
** All terms of the ORDER BY that match against the index must be either
** ASC or DESC.  (Terms of the ORDER BY clause past the end of a UNIQUE
** index do not need to satisfy this constraint.)  The *pbRev value is
** set to 1 if the ORDER BY clause is all DESC and it is set to 0 if
** the ORDER BY clause is all ASC.
*/
/* static int isSortingIndex( */
/*   Parse *pParse,          /1* Parsing context *1/ */
/*   Index *pIdx,            /1* The index we are testing *1/ */
/*   int base,               /1* Cursor number for the table to be sorted *1/ */
/*   ExprList *pOrderBy,     /1* The ORDER BY clause *1/ */
/*   int nEqCol,             /1* Number of index columns with == constraints *1/ */
/*   int *pbRev              /1* Set to 1 if ORDER BY is DESC *1/ */
/* ){ */
/*   int i, j;                       /1* Loop counters *1/ */
/*   int sortOrder = 0;              /1* XOR of index and ORDER BY sort direction *1/ */
/*   int nTerm;                      /1* Number of ORDER BY terms *1/ */
/*   struct ExprList_item *pTerm;    /1* A term of the ORDER BY clause *1/ */
/*   sqlite3 *db = pParse->db; */

/*   assert( pOrderBy!=0 ); */
/*   nTerm = pOrderBy->nExpr; */
/*   assert( nTerm>0 ); */

/*   /1* Match terms of the ORDER BY clause against columns of */
/*   ** the index. */
/*   *1/ */
/*   for(i=j=0, pTerm=pOrderBy->a; j<nTerm && i<pIdx->nColumn; i++){ */
/*     Expr *pExpr;       /1* The expression of the ORDER BY pTerm *1/ */
/*     CollSeq *pColl;    /1* The collating sequence of pExpr *1/ */
/*     int termSortOrder; /1* Sort order for this term *1/ */

/*     pExpr = pTerm->pExpr; */
/*     if( pExpr->op!=TK_COLUMN || pExpr->iTable!=base ){ */
/*       /1* Can not use an index sort on anything that is not a column in the */
/*       ** left-most table of the FROM clause *1/ */
/*       return 0; */
/*     } */
/*     pColl = sqlite3ExprCollSeq(pParse, pExpr); */
/*     if( !pColl ) pColl = db->pDfltColl; */
/*     if( pExpr->iColumn!=pIdx->aiColumn[i] || */
/*         sqlite3StrICmp(pColl->zName, pIdx->azColl[i]) ){ */
/*       /1* Term j of the ORDER BY clause does not match column i of the index *1/ */
/*       if( i<nEqCol ){ */
/*         /1* If an index column that is constrained by == fails to match an */
/*         ** ORDER BY term, that is OK.  Just ignore that column of the index */
/*         *1/ */
/*         continue; */
/*       }else{ */
/*         /1* If an index column fails to match and is not constrained by == */
/*         ** then the index cannot satisfy the ORDER BY constraint. */
/*         *1/ */
/*         return 0; */
/*       } */
/*     } */
/*     assert( pIdx->aSortOrder!=0 ); */
/*     assert( pTerm->sortOrder==0 || pTerm->sortOrder==1 ); */
/*     assert( pIdx->aSortOrder[i]==0 || pIdx->aSortOrder[i]==1 ); */
/*     termSortOrder = pIdx->aSortOrder[i] ^ pTerm->sortOrder; */
/*     if( i>nEqCol ){ */
/*       if( termSortOrder!=sortOrder ){ */
/*         /1* Indices can only be used if all ORDER BY terms past the */
/*         ** equality constraints are all either DESC or ASC. *1/ */
/*         return 0; */
/*       } */
/*     }else{ */
/*       sortOrder = termSortOrder; */
/*     } */
/*     j++; */
/*     pTerm++; */
/*   } */

/*   /1* The index can be used for sorting if all terms of the ORDER BY clause */
/*   ** are covered. */
/*   *1/ */
/*   if( j>=nTerm ){ */
/*     *pbRev = sortOrder!=0; */
/*     return 1; */
/*   } */
/*   return 0; */
/* } */

/*
** Check table to see if the ORDER BY clause in pOrderBy can be satisfied
** by sorting in order of ROWID.  Return true if so and set *pbRev to be
** true for reverse ROWID and false for forward ROWID order.
*/
static int sortableByRowid(
  int base,               /* Cursor number for table to be sorted */
  ExprList *pOrderBy,     /* The ORDER BY clause */
  int *pbRev              /* Set to 1 if ORDER BY is DESC */
){
  Expr *p;

  assert( pOrderBy!=0 );
  assert( pOrderBy->nExpr>0 );
  p = pOrderBy->a[0].pExpr;
  if( pOrderBy->nExpr==1 && p->op==TK_COLUMN && p->iTable==base
          && p->iColumn==-1 ){
    *pbRev = pOrderBy->a[0].sortOrder;
    return 1;
  }
  return 0;
}

/*
** Prepare a crude estimate of the logarithm of the input value.
** The results need not be exact.  This is only used for estimating
** the total cost of performing operatings with O(logN) or O(NlogN)
** complexity.  Because N is just a guess, it is no great tragedy if
** logN is a little off.
*/
static double estLog(double N){
  double logN = 1;
  double x = 10;
  while( N>x ){
    logN += 1;
    x *= 10;
  }
  return logN;
}

/*
** Find the best index for accessing a particular table.  Return a pointer
** to the index, flags that describe how the index should be used, the
** number of equality constraints, and the "cost" for this index.
**
** The lowest cost index wins.  The cost is an estimate of the amount of
** CPU and disk I/O need to process the request using the selected index.
** Factors that influence cost include:
**
**    *  The estimated number of rows that will be retrieved.  (The
**       fewer the better.)
**
**    *  Whether or not sorting must occur.
**
**    *  Whether or not there must be separate lookups in the
**       index and in the main table.
**
*/
/* static double bestIndex( */
/*   Parse *pParse,              /1* The parsing context *1/ */
/*   WhereClause *pWC,           /1* The WHERE clause *1/ */
/*   struct SrcList_item *pSrc,  /1* The FROM clause term to search *1/ */
/*   Bitmask notReady,           /1* Mask of cursors that are not available *1/ */
/*   ExprList *pOrderBy,         /1* The order by clause *1/ */
/*   Index **ppIndex,            /1* Make *ppIndex point to the best index *1/ */
/*   int *pFlags,                /1* Put flags describing this choice in *pFlags *1/ */
/*   int *pnEq                   /1* Put the number of == or IN constraints here *1/ */
/* ){ */
/*   WhereTerm *pTerm; */
/*   Index *bestIdx = 0;         /1* Index that gives the lowest cost *1/ */
/*   double lowestCost;          /1* The cost of using bestIdx *1/ */
/*   int bestFlags = 0;          /1* Flags associated with bestIdx *1/ */
/*   int bestNEq = 0;            /1* Best value for nEq *1/ */
/*   int iCur = pSrc->iCursor;   /1* The cursor of the table to be accessed *1/ */
/*   Index *pProbe;              /1* An index we are evaluating *1/ */
/*   int rev;                    /1* True to scan in reverse order *1/ */
/*   int flags;                  /1* Flags associated with pProbe *1/ */
/*   int nEq;                    /1* Number of == or IN constraints *1/ */
/*   double cost;                /1* Cost of using pProbe *1/ */

/*   TRACE(("bestIndex: tbl=%s notReady=%x\n", pSrc->pTab->zName, notReady)); */
/*   lowestCost = SQLITE_BIG_DBL; */
/*   pProbe = pSrc->pTab->pIndex; */

/*   /1* If the table has no indices and there are no terms in the where */
/*   ** clause that refer to the ROWID, then we will never be able to do */
/*   ** anything other than a full table scan on this table.  We might as */
/*   ** well put it first in the join order.  That way, perhaps it can be */
/*   ** referenced by other tables in the join. */
/*   *1/ */
/*   if( pProbe==0 && */
/*      findTerm(pWC, iCur, -1, 0, WO_EQ|WO_IN|WO_LT|WO_LE|WO_GT|WO_GE,0)==0 && */
/*      (pOrderBy==0 || !sortableByRowid(iCur, pOrderBy, &rev)) ){ */
/*     *pFlags = 0; */
/*     *ppIndex = 0; */
/*     *pnEq = 0; */
/*     return 0.0; */
/*   } */

/*   /1* Check for a rowid=EXPR or rowid IN (...) constraints */
/*   *1/ */
/*   pTerm = findTerm(pWC, iCur, -1, notReady, WO_EQ|WO_IN, 0); */
/*   if( pTerm ){ */
/*     Expr *pExpr; */
/*     *ppIndex = 0; */
/*     bestFlags = WHERE_ROWID_EQ; */
/*     if( pTerm->eOperator & WO_EQ ){ */
/*       /1* Rowid== is always the best pick.  Look no further.  Because only */
/*       ** a single row is generated, output is always in sorted order *1/ */
/*       *pFlags = WHERE_ROWID_EQ | WHERE_UNIQUE; */
/*       *pnEq = 1; */
/*       TRACE(("... best is rowid\n")); */
/*       return 0.0; */
/*     }else if( (pExpr = pTerm->pExpr)->pList!=0 ){ */
/*       /1* Rowid IN (LIST): cost is NlogN where N is the number of list */
/*       ** elements.  *1/ */
/*       lowestCost = pExpr->pList->nExpr; */
/*       lowestCost *= estLog(lowestCost); */
/*     }else{ */
/*       /1* Rowid IN (SELECT): cost is NlogN where N is the number of rows */
/*       ** in the result of the inner select.  We have no way to estimate */
/*       ** that value so make a wild guess. *1/ */
/*       lowestCost = 200; */
/*     } */
/*     TRACE(("... rowid IN cost: %.9g\n", lowestCost)); */
/*   } */

/*   /1* Estimate the cost of a table scan.  If we do not know how many */
/*   ** entries are in the table, use 1 million as a guess. */
/*   *1/ */
/*   cost = pProbe ? pProbe->aiRowEst[0] : 1000000; */
/*   TRACE(("... table scan base cost: %.9g\n", cost)); */
/*   flags = WHERE_ROWID_RANGE; */

/*   /1* Check for constraints on a range of rowids in a table scan. */
/*   *1/ */
/*   pTerm = findTerm(pWC, iCur, -1, notReady, WO_LT|WO_LE|WO_GT|WO_GE, 0); */
/*   if( pTerm ){ */
/*     if( findTerm(pWC, iCur, -1, notReady, WO_LT|WO_LE, 0) ){ */
/*       flags |= WHERE_TOP_LIMIT; */
/*       cost /= 3;  /1* Guess that rowid<EXPR eliminates two-thirds or rows *1/ */
/*     } */
/*     if( findTerm(pWC, iCur, -1, notReady, WO_GT|WO_GE, 0) ){ */
/*       flags |= WHERE_BTM_LIMIT; */
/*       cost /= 3;  /1* Guess that rowid>EXPR eliminates two-thirds of rows *1/ */
/*     } */
/*     TRACE(("... rowid range reduces cost to %.9g\n", cost)); */
/*   }else{ */
/*     flags = 0; */
/*   } */

/*   /1* If the table scan does not satisfy the ORDER BY clause, increase */
/*   ** the cost by NlogN to cover the expense of sorting. *1/ */
/*   if( pOrderBy ){ */
/*     if( sortableByRowid(iCur, pOrderBy, &rev) ){ */
/*       flags |= WHERE_ORDERBY|WHERE_ROWID_RANGE; */
/*       if( rev ){ */
/*         flags |= WHERE_REVERSE; */
/*       } */
/*     }else{ */
/*       cost += cost*estLog(cost); */
/*       TRACE(("... sorting increases cost to %.9g\n", cost)); */
/*     } */
/*   } */
/*   if( cost<lowestCost ){ */
/*     lowestCost = cost; */
/*     bestFlags = flags; */
/*   } */

/*   /1* Look at each index. */
/*   *1/ */
/*   for(; pProbe; pProbe=pProbe->pNext){ */
/*     int i;                       /1* Loop counter *1/ */
/*     double inMultiplier = 1; */

/*     TRACE(("... index %s:\n", pProbe->zName)); */

/*     /1* Count the number of columns in the index that are satisfied */
/*     ** by x=EXPR constraints or x IN (...) constraints. */
/*     *1/ */
/*     flags = 0; */
/*     for(i=0; i<pProbe->nColumn; i++){ */
/*       int j = pProbe->aiColumn[i]; */
/*       pTerm = findTerm(pWC, iCur, j, notReady, WO_EQ|WO_IN, pProbe); */
/*       if( pTerm==0 ) break; */
/*       flags |= WHERE_COLUMN_EQ; */
/*       if( pTerm->eOperator & WO_IN ){ */
/*         Expr *pExpr = pTerm->pExpr; */
/*         flags |= WHERE_COLUMN_IN; */
/*         if( pExpr->pSelect!=0 ){ */
/*           inMultiplier *= 100; */
/*         }else if( pExpr->pList!=0 ){ */
/*           inMultiplier *= pExpr->pList->nExpr + 1; */
/*         } */
/*       } */
/*     } */
/*     cost = pProbe->aiRowEst[i] * inMultiplier * estLog(inMultiplier); */
/*     nEq = i; */
/*     if( pProbe->onError!=OE_None && (flags & WHERE_COLUMN_IN)==0 */
/*          && nEq==pProbe->nColumn ){ */
/*       flags |= WHERE_UNIQUE; */
/*     } */
/*     TRACE(("...... nEq=%d inMult=%.9g cost=%.9g\n", nEq, inMultiplier, cost)); */

/*     /1* Look for range constraints */
/*     *1/ */
/*     if( nEq<pProbe->nColumn ){ */
/*       int j = pProbe->aiColumn[nEq]; */
/*       pTerm = findTerm(pWC, iCur, j, notReady, WO_LT|WO_LE|WO_GT|WO_GE, pProbe); */
/*       if( pTerm ){ */
/*         flags |= WHERE_COLUMN_RANGE; */
/*         if( findTerm(pWC, iCur, j, notReady, WO_LT|WO_LE, pProbe) ){ */
/*           flags |= WHERE_TOP_LIMIT; */
/*           cost /= 3; */
/*         } */
/*         if( findTerm(pWC, iCur, j, notReady, WO_GT|WO_GE, pProbe) ){ */
/*           flags |= WHERE_BTM_LIMIT; */
/*           cost /= 3; */
/*         } */
/*         TRACE(("...... range reduces cost to %.9g\n", cost)); */
/*       } */
/*     } */

/*     /1* Add the additional cost of sorting if that is a factor. */
/*     *1/ */
/*     if( pOrderBy ){ */
/*       if( (flags & WHERE_COLUMN_IN)==0 && */
/*            isSortingIndex(pParse,pProbe,iCur,pOrderBy,nEq,&rev) ){ */
/*         if( flags==0 ){ */
/*           flags = WHERE_COLUMN_RANGE; */
/*         } */
/*         flags |= WHERE_ORDERBY; */
/*         if( rev ){ */
/*           flags |= WHERE_REVERSE; */
/*         } */
/*       }else{ */
/*         cost += cost*estLog(cost); */
/*         TRACE(("...... orderby increases cost to %.9g\n", cost)); */
/*       } */
/*     } */

/*     /1* Check to see if we can get away with using just the index without */
/*     ** ever reading the table.  If that is the case, then halve the */
/*     ** cost of this index. */
/*     *1/ */
/*     if( flags && pSrc->colUsed < (((Bitmask)1)<<(BMS-1)) ){ */
/*       Bitmask m = pSrc->colUsed; */
/*       int j; */
/*       for(j=0; j<pProbe->nColumn; j++){ */
/*         int x = pProbe->aiColumn[j]; */
/*         if( x<BMS-1 ){ */
/*           m &= ~(((Bitmask)1)<<x); */
/*         } */
/*       } */
/*       if( m==0 ){ */
/*         flags |= WHERE_IDX_ONLY; */
/*         cost /= 2; */
/*         TRACE(("...... idx-only reduces cost to %.9g\n", cost)); */
/*       } */
/*     } */

/*     /1* If this index has achieved the lowest cost so far, then use it. */
/*     *1/ */
/*     if( cost < lowestCost ){ */
/*       bestIdx = pProbe; */
/*       lowestCost = cost; */
/*       assert( flags!=0 ); */
/*       bestFlags = flags; */
/*       bestNEq = nEq; */
/*     } */
/*   } */

/*   /1* Report the best result */
/*   *1/ */
/*   *ppIndex = bestIdx; */
/*   TRACE(("best index is %s, cost=%.9g, flags=%x, nEq=%d\n", */
/*         bestIdx ? bestIdx->zName : "(none)", lowestCost, bestFlags, bestNEq)); */
/*   *pFlags = bestFlags; */
/*   *pnEq = bestNEq; */
/*   return lowestCost; */
/* } */


/*
** Disable a term in the WHERE clause.  Except, do not disable the term
** if it controls a LEFT OUTER JOIN and it did not originate in the ON
** or USING clause of that join.
**
** Consider the term t2.z='ok' in the following queries:
**
**   (1)  SELECT * FROM t1 LEFT JOIN t2 ON t1.a=t2.x WHERE t2.z='ok'
**   (2)  SELECT * FROM t1 LEFT JOIN t2 ON t1.a=t2.x AND t2.z='ok'
**   (3)  SELECT * FROM t1, t2 WHERE t1.a=t2.x AND t2.z='ok'
**
** The t2.z='ok' is disabled in the in (2) because it originates
** in the ON clause.  The term is disabled in (3) because it is not part
** of a LEFT OUTER JOIN.  In (1), the term is not disabled.
**
** Disabling a term causes that term to not be tested in the inner loop
** of the join.  Disabling is an optimization.  When terms are satisfied
** by indices, we disable them to prevent redundant tests in the inner
** loop.  We would get the correct results if nothing were ever disabled,
** but joins might run a little slower.  The trick is to disable as much
** as we can without disabling too much.  If we disabled in (1), we'd get
** the wrong answer.  See ticket #813.
*/
static void disableTerm(WhereLevel *pLevel, WhereTerm *pTerm){
  if( pTerm
      && (pTerm->flags & TERM_CODED)==0
      && (pLevel->iLeftJoin==0 || ExprHasProperty(pTerm->pExpr, EP_FromJoin))
  ){
    pTerm->flags |= TERM_CODED;
    if( pTerm->iParent>=0 ){
      WhereTerm *pOther = &pTerm->pWC->a[pTerm->iParent];
      if( (--pOther->nChild)==0 ){
        disableTerm(pLevel, pOther);
      }
    }
  }
}

/*
** Generate code that builds a probe for an index.  Details:
**
**    *  Check the top nColumn entries on the stack.  If any
**       of those entries are NULL, jump immediately to brk,
**       which is the loop exit, since no index entry will match
**       if any part of the key is NULL. Pop (nColumn+nExtra)
**       elements from the stack.
**
**    *  Construct a probe entry from the top nColumn entries in
**       the stack with affinities appropriate for index pIdx.
**       Only nColumn elements are popped from the stack in this case
**       (by OP_MakeRecord).
**
*/
/* static void buildIndexProbe( */
/*   Vdbe *v, */
/*   int nColumn, */
/*   int nExtra, */
/*   int brk, */
/*   Index *pIdx */
/* ){ */
/*   sqlite3VdbeAddOp(v, OP_NotNull, -nColumn, sqlite3VdbeCurrentAddr(v)+3); */
/*   sqlite3VdbeAddOp(v, OP_Pop, nColumn+nExtra, 0); */
/*   sqlite3VdbeAddOp(v, OP_Goto, 0, brk); */
/*   sqlite3VdbeAddOp(v, OP_MakeRecord, nColumn, 0); */
/*   sqlite3IndexAffinityStr(v, pIdx); */
/* } */


/*
** Generate code for a single equality term of the WHERE clause.  An equality
** term can be either X=expr or X IN (...).   pTerm is the term to be
** coded.
**
** The current value for the constraint is left on the top of the stack.
**
** For a constraint of the form X=expr, the expression is evaluated and its
** result is left on the stack.  For constraints of the form X IN (...)
** this routine sets up a loop that will iterate over all values of X.
*/
/* static void codeEqualityTerm( */
/*   Parse *pParse,      /1* The parsing context *1/ */
/*   WhereTerm *pTerm,   /1* The term of the WHERE clause to be coded *1/ */
/*   int brk,            /1* Jump here to abandon the loop *1/ */
/*   WhereLevel *pLevel  /1* When level of the FROM clause we are working on *1/ */
/* ){ */
/*   Expr *pX = pTerm->pExpr; */
/*   if( pX->op!=TK_IN ){ */
/*     assert( pX->op==TK_EQ ); */
/*     sqlite3ExprCode(pParse, pX->pRight); */
/* #ifndef SQLITE_OMIT_SUBQUERY */
/*   }else{ */
/*     int iTab; */
/*     int *aIn; */
/*     Vdbe *v = pParse->pVdbe; */

/*     sqlite3CodeSubselect(pParse, pX); */
/*     iTab = pX->iTable; */
/*     sqlite3VdbeAddOp(v, OP_Rewind, iTab, brk); */
/*     VdbeComment((v, "# %.*s", pX->span.n, pX->span.z)); */
/*     pLevel->nIn++; */
/*     sqliteReallocOrFree((void**)&pLevel->aInLoop, */
/*                                  sizeof(pLevel->aInLoop[0])*3*pLevel->nIn); */
/*     aIn = pLevel->aInLoop; */
/*     if( aIn ){ */
/*       aIn += pLevel->nIn*3 - 3; */
/*       aIn[0] = OP_Next; */
/*       aIn[1] = iTab; */
/*       aIn[2] = sqlite3VdbeAddOp(v, OP_Column, iTab, 0); */
/*     }else{ */
/*       pLevel->nIn = 0; */
/*     } */
/* #endif */
/*   } */
/*   disableTerm(pLevel, pTerm); */
/* } */

/*
** Generate code that will evaluate all == and IN constraints for an
** index.  The values for all constraints are left on the stack.
**
** For example, consider table t1(a,b,c,d,e,f) with index i1(a,b,c).
** Suppose the WHERE clause is this:  a==5 AND b IN (1,2,3) AND c>5 AND c<10
** The index has as many as three equality constraints, but in this
** example, the third "c" value is an inequality.  So only two
** constraints are coded.  This routine will generate code to evaluate
** a==5 and b IN (1,2,3).  The current values for a and b will be left
** on the stack - a is the deepest and b the shallowest.
**
** In the example above nEq==2.  But this subroutine works for any value
** of nEq including 0.  If nEq==0, this routine is nearly a no-op.
** The only thing it does is allocate the pLevel->iMem memory cell.
**
** This routine always allocates at least one memory cell and puts
** the address of that memory cell in pLevel->iMem.  The code that
** calls this routine will use pLevel->iMem to store the termination
** key value of the loop.  If one or more IN operators appear, then
** this routine allocates an additional nEq memory cells for internal
** use.
*/
/* static void codeAllEqualityTerms( */
/*   Parse *pParse,        /1* Parsing context *1/ */
/*   WhereLevel *pLevel,   /1* Which nested loop of the FROM we are coding *1/ */
/*   WhereClause *pWC,     /1* The WHERE clause *1/ */
/*   Bitmask notReady,     /1* Which parts of FROM have not yet been coded *1/ */
/*   int brk               /1* Jump here to end the loop *1/ */
/* ){ */
/*   int nEq = pLevel->nEq;        /1* The number of == or IN constraints to code *1/ */
/*   int termsInMem = 0;           /1* If true, store value in mem[] cells *1/ */
/*   Vdbe *v = pParse->pVdbe;      /1* The virtual machine under construction *1/ */
/*   Index *pIdx = pLevel->pIdx;   /1* The index being used for this loop *1/ */
/*   int iCur = pLevel->iTabCur;   /1* The cursor of the table *1/ */
/*   WhereTerm *pTerm;             /1* A single constraint term *1/ */
/*   int j;                        /1* Loop counter *1/ */

/*   /1* Figure out how many memory cells we will need then allocate them. */
/*   ** We always need at least one used to store the loop terminator */
/*   ** value.  If there are IN operators we'll need one for each == or */
/*   ** IN constraint. */
/*   *1/ */
/*   pLevel->iMem = pParse->nMem++; */
/*   if( pLevel->flags & WHERE_COLUMN_IN ){ */
/*     pParse->nMem += pLevel->nEq; */
/*     termsInMem = 1; */
/*   } */

/*   /1* Evaluate the equality constraints */
/*   *1/ */
/*   for(j=0; j<pIdx->nColumn; j++){ */
/*     int k = pIdx->aiColumn[j]; */
/*     pTerm = findTerm(pWC, iCur, k, notReady, WO_EQ|WO_IN, pIdx); */
/*     if( pTerm==0 ) break; */
/*     assert( (pTerm->flags & TERM_CODED)==0 ); */
/*     codeEqualityTerm(pParse, pTerm, brk, pLevel); */
/*     if( termsInMem ){ */
/*       sqlite3VdbeAddOp(v, OP_MemStore, pLevel->iMem+j+1, 1); */
/*     } */
/*   } */
/*   assert( j==nEq ); */

/*   /1* Make sure all the constraint values are on the top of the stack */
/*   *1/ */
/*   if( termsInMem ){ */
/*     for(j=0; j<nEq; j++){ */
/*       sqlite3VdbeAddOp(v, OP_MemLoad, pLevel->iMem+j+1, 0); */
/*     } */
/*   } */
/* } */

#if defined(SQLITE_TEST)
/*
** The following variable holds a text description of query plan generated
** by the most recent call to sqlite3WhereBegin().  Each call to WhereBegin
** overwrites the previous.  This information is used for testing and
** analysis only.
*/
char sqlite3_query_plan[BMS*2*40];  /* Text of the join */
static int nQPlan = 0;              /* Next free slow in _query_plan[] */

#endif /* SQLITE_TEST */



/*
** Generate the beginning of the loop used for WHERE clause processing.
** The return value is a pointer to an opaque structure that contains
** information needed to terminate the loop.  Later, the calling routine
** should invoke sqlite3WhereEnd() with the return value of this function
** in order to complete the WHERE clause processing.
**
** If an error occurs, this routine returns NULL.
**
** The basic idea is to do a nested loop, one loop for each table in
** the FROM clause of a select.  (INSERT and UPDATE statements are the
** same as a SELECT with only a single table in the FROM clause.)  For
** example, if the SQL is this:
**
**       SELECT * FROM t1, t2, t3 WHERE ...;
**
** Then the code generated is conceptually like the following:
**
**      foreach row1 in t1 do       \    Code generated
**        foreach row2 in t2 do      |-- by sqlite3WhereBegin()
**          foreach row3 in t3 do   /
**            ...
**          end                     \    Code generated
**        end                        |-- by sqlite3WhereEnd()
**      end                         /
**
** Note that the loops might not be nested in the order in which they
** appear in the FROM clause if a different order is better able to make
** use of indices.  Note also that when the IN operator appears in
** the WHERE clause, it might result in additional nested loops for
** scanning through all values on the right-hand side of the IN.
**
** There are Btree cursors associated with each table.  t1 uses cursor
** number pTabList->a[0].iCursor.  t2 uses the cursor pTabList->a[1].iCursor.
** And so forth.  This routine generates code to open those VDBE cursors
** and sqlite3WhereEnd() generates the code to close them.
**
** The code that sqlite3WhereBegin() generates leaves the cursors named
** in pTabList pointing at their appropriate entries.  The [...] code
** can use OP_Column and OP_Rowid opcodes on these cursors to extract
** data from the various tables of the loop.
**
** If the WHERE clause is empty, the foreach loops must each scan their
** entire tables.  Thus a three-way join is an O(N^3) operation.  But if
** the tables have indices and there are terms in the WHERE clause that
** refer to those indices, a complete table scan can be avoided and the
** code will run much faster.  Most of the work of this routine is checking
** to see if there are indices that can be used to speed up the loop.
**
** Terms of the WHERE clause are also used to limit which rows actually
** make it to the "..." in the middle of the loop.  After each "foreach",
** terms of the WHERE clause that use only terms in that loop and outer
** loops are evaluated and if false a jump is made around all subsequent
** inner loops (or around the "..." if the test occurs within the inner-
** most loop)
**
** OUTER JOINS
**
** An outer join of tables t1 and t2 is conceptally coded as follows:
**
**    foreach row1 in t1 do
**      flag = 0
**      foreach row2 in t2 do
**        start:
**          ...
**          flag = 1
**      end
**      if flag==0 then
**        move the row2 cursor to a null row
**        goto start
**      fi
**    end
**
** ORDER BY CLAUSE PROCESSING
**
** *ppOrderBy is a pointer to the ORDER BY clause of a SELECT statement,
** if there is one.  If there is no ORDER BY clause or if this routine
** is called from an UPDATE or DELETE statement, then ppOrderBy is NULL.
**
** If an index can be used so that the natural output order of the table
** scan is correct for the ORDER BY clause, then that index is used and
** *ppOrderBy is set to NULL.  This is an optimization that prevents an
** unnecessary sort of the result set if an index appropriate for the
** ORDER BY clause already exists.
**
** If the where clause loops cannot be arranged to provide the correct
** output order, then the *ppOrderBy is unchanged.
*/
/* WhereInfo *sqlite3WhereBegin( */
/*   Parse *pParse,        /1* The parser context *1/ */
/*   SrcList *pTabList,    /1* A list of all tables to be scanned *1/ */
/*   Expr *pWhere,         /1* The WHERE clause *1/ */
/*   ExprList **ppOrderBy  /1* An ORDER BY clause, or NULL *1/ */
/* ){ */
/*   int i;                     /1* Loop counter *1/ */
/*   WhereInfo *pWInfo;         /1* Will become the return value of this function *1/ */
/*   Vdbe *v = pParse->pVdbe;   /1* The virtual database engine *1/ */
/*   int brk, cont = 0;         /1* Addresses used during code generation *1/ */
/*   Bitmask notReady;          /1* Cursors that are not yet positioned *1/ */
/*   WhereTerm *pTerm;          /1* A single term in the WHERE clause *1/ */
/*   ExprMaskSet maskSet;       /1* The expression mask set *1/ */
/*   WhereClause wc;            /1* The WHERE clause is divided into these terms *1/ */
/*   struct SrcList_item *pTabItem;  /1* A single entry from pTabList *1/ */
/*   WhereLevel *pLevel;             /1* A single level in the pWInfo list *1/ */
/*   int iFrom;                      /1* First unused FROM clause element *1/ */
/*   int andFlags;              /1* AND-ed combination of all wc.a[].flags *1/ */

/*   /1* The number of tables in the FROM clause is limited by the number of */
/*   ** bits in a Bitmask */
/*   *1/ */
/*   if( pTabList->nSrc>BMS ){ */
/*     sqlite3ErrorMsg(pParse, "at most %d tables in a join", BMS); */
/*     return 0; */
/*   } */

/*   /1* Split the WHERE clause into separate subexpressions where each */
/*   ** subexpression is separated by an AND operator. */
/*   *1/ */
/*   initMaskSet(&maskSet); */
/*   whereClauseInit(&wc, pParse); */
/*   whereSplit(&wc, pWhere, TK_AND); */

/*   /1* Allocate and initialize the WhereInfo structure that will become the */
/*   ** return value. */
/*   *1/ */
/*   pWInfo = sqliteMalloc( sizeof(WhereInfo) + pTabList->nSrc*sizeof(WhereLevel)); */
/*   if( sqlite3MallocFailed() ){ */
/*     goto whereBeginNoMem; */
/*   } */
/*   pWInfo->pParse = pParse; */
/*   pWInfo->pTabList = pTabList; */
/*   pWInfo->iBreak = sqlite3VdbeMakeLabel(v); */

/*   /1* Special case: a WHERE clause that is constant.  Evaluate the */
/*   ** expression and either jump over all of the code or fall thru. */
/*   *1/ */
/*   if( pWhere && (pTabList->nSrc==0 || sqlite3ExprIsConstant(pWhere)) ){ */
/*     sqlite3ExprIfFalse(pParse, pWhere, pWInfo->iBreak, 1); */
/*     pWhere = 0; */
/*   } */

/*   /1* Analyze all of the subexpressions.  Note that exprAnalyze() might */
/*   ** add new virtual terms onto the end of the WHERE clause.  We do not */
/*   ** want to analyze these virtual terms, so start analyzing at the end */
/*   ** and work forward so that the added virtual terms are never processed. */
/*   *1/ */
/*   for(i=0; i<pTabList->nSrc; i++){ */
/*     createMask(&maskSet, pTabList->a[i].iCursor); */
/*   } */
/*   exprAnalyzeAll(pTabList, &maskSet, &wc); */
/*   if( sqlite3MallocFailed() ){ */
/*     goto whereBeginNoMem; */
/*   } */

/*   /1* Chose the best index to use for each table in the FROM clause. */
/*   ** */
/*   ** This loop fills in the following fields: */
/*   ** */
/*   **   pWInfo->a[].pIdx      The index to use for this level of the loop. */
/*   **   pWInfo->a[].flags     WHERE_xxx flags associated with pIdx */
/*   **   pWInfo->a[].nEq       The number of == and IN constraints */
/*   **   pWInfo->a[].iFrom     When term of the FROM clause is being coded */
/*   **   pWInfo->a[].iTabCur   The VDBE cursor for the database table */
/*   **   pWInfo->a[].iIdxCur   The VDBE cursor for the index */
/*   ** */
/*   ** This loop also figures out the nesting order of tables in the FROM */
/*   ** clause. */
/*   *1/ */
/*   notReady = ~(Bitmask)0; */
/*   pTabItem = pTabList->a; */
/*   pLevel = pWInfo->a; */
/*   andFlags = ~0; */
/*   TRACE(("*** Optimizer Start ***\n")); */
/*   for(i=iFrom=0, pLevel=pWInfo->a; i<pTabList->nSrc; i++, pLevel++){ */
/*     Index *pIdx;                /1* Index for FROM table at pTabItem *1/ */
/*     int flags;                  /1* Flags asssociated with pIdx *1/ */
/*     int nEq;                    /1* Number of == or IN constraints *1/ */
/*     double cost;                /1* The cost for pIdx *1/ */
/*     int j;                      /1* For looping over FROM tables *1/ */
/*     Index *pBest = 0;           /1* The best index seen so far *1/ */
/*     int bestFlags = 0;          /1* Flags associated with pBest *1/ */
/*     int bestNEq = 0;            /1* nEq associated with pBest *1/ */
/*     double lowestCost;          /1* Cost of the pBest *1/ */
/*     int bestJ = 0;              /1* The value of j *1/ */
/*     Bitmask m;                  /1* Bitmask value for j or bestJ *1/ */
/*     int once = 0;               /1* True when first table is seen *1/ */

/*     lowestCost = SQLITE_BIG_DBL; */
/*     for(j=iFrom, pTabItem=&pTabList->a[j]; j<pTabList->nSrc; j++, pTabItem++){ */
/*       if( once && */
/*           ((pTabItem->jointype & (JT_LEFT|JT_CROSS))!=0 */
/*            || (j>0 && (pTabItem[-1].jointype & (JT_LEFT|JT_CROSS))!=0)) */
/*       ){ */
/*         break; */
/*       } */
/*       m = getMask(&maskSet, pTabItem->iCursor); */
/*       if( (m & notReady)==0 ){ */
/*         if( j==iFrom ) iFrom++; */
/*         continue; */
/*       } */
/*       cost = bestIndex(pParse, &wc, pTabItem, notReady, */
/*                        (i==0 && ppOrderBy) ? *ppOrderBy : 0, */
/*                        &pIdx, &flags, &nEq); */
/*       if( cost<lowestCost ){ */
/*         once = 1; */
/*         lowestCost = cost; */
/*         pBest = pIdx; */
/*         bestFlags = flags; */
/*         bestNEq = nEq; */
/*         bestJ = j; */
/*       } */
/*     } */
/*     TRACE(("*** Optimizer choose table %d for loop %d\n", bestJ, */
/*            pLevel-pWInfo->a)); */
/*     if( (bestFlags & WHERE_ORDERBY)!=0 ){ */
/*       *ppOrderBy = 0; */
/*     } */
/*     andFlags &= bestFlags; */
/*     pLevel->flags = bestFlags; */
/*     pLevel->pIdx = pBest; */
/*     pLevel->nEq = bestNEq; */
/*     pLevel->aInLoop = 0; */
/*     pLevel->nIn = 0; */
/*     if( pBest ){ */
/*       pLevel->iIdxCur = pParse->nTab++; */
/*     }else{ */
/*       pLevel->iIdxCur = -1; */
/*     } */
/*     notReady &= ~getMask(&maskSet, pTabList->a[bestJ].iCursor); */
/*     pLevel->iFrom = bestJ; */
/*   } */
/*   TRACE(("*** Optimizer Finished ***\n")); */

/*   /1* If the total query only selects a single row, then the ORDER BY */
/*   ** clause is irrelevant. */
/*   *1/ */
/*   if( (andFlags & WHERE_UNIQUE)!=0 && ppOrderBy ){ */
/*     *ppOrderBy = 0; */
/*   } */

/*   /1* Open all tables in the pTabList and any indices selected for */
/*   ** searching those tables. */
/*   *1/ */
/*   sqlite3CodeVerifySchema(pParse, -1); /1* Insert the cookie verifier Goto *1/ */
/*   pLevel = pWInfo->a; */
/*   for(i=0, pLevel=pWInfo->a; i<pTabList->nSrc; i++, pLevel++){ */
/*     Table *pTab;     /1* Table to open *1/ */
/*     Index *pIx;      /1* Index used to access pTab (if any) *1/ */
/*     int iDb;         /1* Index of database containing table/index *1/ */
/*     int iIdxCur = pLevel->iIdxCur; */

/* #ifndef SQLITE_OMIT_EXPLAIN */
/*     if( pParse->explain==2 ){ */
/*       char *zMsg; */
/*       struct SrcList_item *pItem = &pTabList->a[pLevel->iFrom]; */
/*       zMsg = sqlite3MPrintf("TABLE %s", pItem->zName); */
/*       if( pItem->zAlias ){ */
/*         zMsg = sqlite3MPrintf("%z AS %s", zMsg, pItem->zAlias); */
/*       } */
/*       if( (pIx = pLevel->pIdx)!=0 ){ */
/*         zMsg = sqlite3MPrintf("%z WITH INDEX %s", zMsg, pIx->zName); */
/*       }else if( pLevel->flags & (WHERE_ROWID_EQ|WHERE_ROWID_RANGE) ){ */
/*         zMsg = sqlite3MPrintf("%z USING PRIMARY KEY", zMsg); */
/*       } */
/*       sqlite3VdbeOp3(v, OP_Explain, i, pLevel->iFrom, zMsg, P3_DYNAMIC); */
/*     } */
/* #endif /1* SQLITE_OMIT_EXPLAIN *1/ */
/*     pTabItem = &pTabList->a[pLevel->iFrom]; */
/*     pTab = pTabItem->pTab; */
/*     iDb = sqlite3SchemaToIndex(pParse->db, pTab->pSchema); */
/*     if( pTab->isTransient || pTab->pSelect ) continue; */
/*     if( (pLevel->flags & WHERE_IDX_ONLY)==0 ){ */
/*       sqlite3OpenTable(pParse, pTabItem->iCursor, iDb, pTab, OP_OpenRead); */
/*       if( pTab->nCol<(sizeof(Bitmask)*8) ){ */
/*         Bitmask b = pTabItem->colUsed; */
/*         int n = 0; */
/*         for(; b; b=b>>1, n++){} */
/*         sqlite3VdbeChangeP2(v, sqlite3VdbeCurrentAddr(v)-1, n); */
/*         assert( n<=pTab->nCol ); */
/*       } */
/*     }else{ */
/*       sqlite3TableLock(pParse, iDb, pTab->tnum, 0, pTab->zName); */
/*     } */
/*     pLevel->iTabCur = pTabItem->iCursor; */
/*     if( (pIx = pLevel->pIdx)!=0 ){ */
/*       KeyInfo *pKey = sqlite3IndexKeyinfo(pParse, pIx); */
/*       assert( pIx->pSchema==pTab->pSchema ); */
/*       sqlite3VdbeAddOp(v, OP_Integer, iDb, 0); */
/*       VdbeComment((v, "# %s", pIx->zName)); */
/*       sqlite3VdbeOp3(v, OP_OpenRead, iIdxCur, pIx->tnum, */
/*                      (char*)pKey, P3_KEYINFO_HANDOFF); */
/*     } */
/*     if( (pLevel->flags & WHERE_IDX_ONLY)!=0 ){ */
/*       sqlite3VdbeAddOp(v, OP_SetNumColumns, iIdxCur, pIx->nColumn+1); */
/*     } */
/*     sqlite3CodeVerifySchema(pParse, iDb); */
/*   } */
/*   pWInfo->iTop = sqlite3VdbeCurrentAddr(v); */

/*   /1* Generate the code to do the search.  Each iteration of the for */
/*   ** loop below generates code for a single nested loop of the VM */
/*   ** program. */
/*   *1/ */
/*   notReady = ~(Bitmask)0; */
/*   for(i=0, pLevel=pWInfo->a; i<pTabList->nSrc; i++, pLevel++){ */
/*     int j; */
/*     int iCur = pTabItem->iCursor;  /1* The VDBE cursor for the table *1/ */
/*     Index *pIdx;       /1* The index we will be using *1/ */
/*     int iIdxCur;       /1* The VDBE cursor for the index *1/ */
/*     int omitTable;     /1* True if we use the index only *1/ */
/*     int bRev;          /1* True if we need to scan in reverse order *1/ */

/*     pTabItem = &pTabList->a[pLevel->iFrom]; */
/*     iCur = pTabItem->iCursor; */
/*     pIdx = pLevel->pIdx; */
/*     iIdxCur = pLevel->iIdxCur; */
/*     bRev = (pLevel->flags & WHERE_REVERSE)!=0; */
/*     omitTable = (pLevel->flags & WHERE_IDX_ONLY)!=0; */

/*     /1* Create labels for the "break" and "continue" instructions */
/*     ** for the current loop.  Jump to brk to break out of a loop. */
/*     ** Jump to cont to go immediately to the next iteration of the */
/*     ** loop. */
/*     *1/ */
/*     brk = pLevel->brk = sqlite3VdbeMakeLabel(v); */
/*     cont = pLevel->cont = sqlite3VdbeMakeLabel(v); */

/*     /1* If this is the right table of a LEFT OUTER JOIN, allocate and */
/*     ** initialize a memory cell that records if this table matches any */
/*     ** row of the left table of the join. */
/*     *1/ */
/*     if( pLevel->iFrom>0 && (pTabItem[-1].jointype & JT_LEFT)!=0 ){ */
/*       if( !pParse->nMem ) pParse->nMem++; */
/*       pLevel->iLeftJoin = pParse->nMem++; */
/*       sqlite3VdbeAddOp(v, OP_MemInt, 0, pLevel->iLeftJoin); */
/*       VdbeComment((v, "# init LEFT JOIN no-match flag")); */
/*     } */

/*     if( pLevel->flags & WHERE_ROWID_EQ ){ */
/*       /1* Case 1:  We can directly reference a single row using an */
/*       **          equality comparison against the ROWID field.  Or */
/*       **          we reference multiple rows using a "rowid IN (...)" */
/*       **          construct. */
/*       *1/ */
/*       pTerm = findTerm(&wc, iCur, -1, notReady, WO_EQ|WO_IN, 0); */
/*       assert( pTerm!=0 ); */
/*       assert( pTerm->pExpr!=0 ); */
/*       assert( pTerm->leftCursor==iCur ); */
/*       assert( omitTable==0 ); */
/*       codeEqualityTerm(pParse, pTerm, brk, pLevel); */
/*       sqlite3VdbeAddOp(v, OP_MustBeInt, 1, brk); */
/*       sqlite3VdbeAddOp(v, OP_NotExists, iCur, brk); */
/*       VdbeComment((v, "pk")); */
/*       pLevel->op = OP_Noop; */
/*     }else if( pLevel->flags & WHERE_ROWID_RANGE ){ */
/*       /1* Case 2:  We have an inequality comparison against the ROWID field. */
/*       *1/ */
/*       int testOp = OP_Noop; */
/*       int start; */
/*       WhereTerm *pStart, *pEnd; */

/*       assert( omitTable==0 ); */
/*       pStart = findTerm(&wc, iCur, -1, notReady, WO_GT|WO_GE, 0); */
/*       pEnd = findTerm(&wc, iCur, -1, notReady, WO_LT|WO_LE, 0); */
/*       if( bRev ){ */
/*         pTerm = pStart; */
/*         pStart = pEnd; */
/*         pEnd = pTerm; */
/*       } */
/*       if( pStart ){ */
/*         Expr *pX; */
/*         pX = pStart->pExpr; */
/*         assert( pX!=0 ); */
/*         assert( pStart->leftCursor==iCur ); */
/*         sqlite3ExprCode(pParse, pX->pRight); */
/*         sqlite3VdbeAddOp(v, OP_ForceInt, pX->op==TK_LE || pX->op==TK_GT, brk); */
/*         sqlite3VdbeAddOp(v, bRev ? OP_MoveLt : OP_MoveGe, iCur, brk); */
/*         VdbeComment((v, "pk")); */
/*         disableTerm(pLevel, pStart); */
/*       }else{ */
/*         sqlite3VdbeAddOp(v, bRev ? OP_Last : OP_Rewind, iCur, brk); */
/*       } */
/*       if( pEnd ){ */
/*         Expr *pX; */
/*         pX = pEnd->pExpr; */
/*         assert( pX!=0 ); */
/*         assert( pEnd->leftCursor==iCur ); */
/*         sqlite3ExprCode(pParse, pX->pRight); */
/*         pLevel->iMem = pParse->nMem++; */
/*         sqlite3VdbeAddOp(v, OP_MemStore, pLevel->iMem, 1); */
/*         if( pX->op==TK_LT || pX->op==TK_GT ){ */
/*           testOp = bRev ? OP_Le : OP_Ge; */
/*         }else{ */
/*           testOp = bRev ? OP_Lt : OP_Gt; */
/*         } */
/*         disableTerm(pLevel, pEnd); */
/*       } */
/*       start = sqlite3VdbeCurrentAddr(v); */
/*       pLevel->op = bRev ? OP_Prev : OP_Next; */
/*       pLevel->p1 = iCur; */
/*       pLevel->p2 = start; */
/*       if( testOp!=OP_Noop ){ */
/*         sqlite3VdbeAddOp(v, OP_Rowid, iCur, 0); */
/*         sqlite3VdbeAddOp(v, OP_MemLoad, pLevel->iMem, 0); */
/*         sqlite3VdbeAddOp(v, testOp, SQLITE_AFF_NUMERIC, brk); */
/*       } */
/*     }else if( pLevel->flags & WHERE_COLUMN_RANGE ){ */
/*       /1* Case 3: The WHERE clause term that refers to the right-most */
/*       **         column of the index is an inequality.  For example, if */
/*       **         the index is on (x,y,z) and the WHERE clause is of the */
/*       **         form "x=5 AND y<10" then this case is used.  Only the */
/*       **         right-most column can be an inequality - the rest must */
/*       **         use the "==" and "IN" operators. */
/*       ** */
/*       **         This case is also used when there are no WHERE clause */
/*       **         constraints but an index is selected anyway, in order */
/*       **         to force the output order to conform to an ORDER BY. */
/*       *1/ */
/*       int start; */
/*       int nEq = pLevel->nEq; */
/*       int topEq=0;        /1* True if top limit uses ==. False is strictly < *1/ */
/*       int btmEq=0;        /1* True if btm limit uses ==. False if strictly > *1/ */
/*       int topOp, btmOp;   /1* Operators for the top and bottom search bounds *1/ */
/*       int testOp; */
/*       int nNotNull;       /1* Number of rows of index that must be non-NULL *1/ */
/*       int topLimit = (pLevel->flags & WHERE_TOP_LIMIT)!=0; */
/*       int btmLimit = (pLevel->flags & WHERE_BTM_LIMIT)!=0; */

/*       /1* Generate code to evaluate all constraint terms using == or IN */
/*       ** and level the values of those terms on the stack. */
/*       *1/ */
/*       codeAllEqualityTerms(pParse, pLevel, &wc, notReady, brk); */

/*       /1* Duplicate the equality term values because they will all be */
/*       ** used twice: once to make the termination key and once to make the */
/*       ** start key. */
/*       *1/ */
/*       for(j=0; j<nEq; j++){ */
/*         sqlite3VdbeAddOp(v, OP_Dup, nEq-1, 0); */
/*       } */

/*       /1* Figure out what comparison operators to use for top and bottom */
/*       ** search bounds. For an ascending index, the bottom bound is a > or >= */
/*       ** operator and the top bound is a < or <= operator.  For a descending */
/*       ** index the operators are reversed. */
/*       *1/ */
/*       nNotNull = nEq + topLimit; */
/*       if( pIdx->aSortOrder[nEq]==SQLITE_SO_ASC ){ */
/*         topOp = WO_LT|WO_LE; */
/*         btmOp = WO_GT|WO_GE; */
/*       }else{ */
/*         topOp = WO_GT|WO_GE; */
/*         btmOp = WO_LT|WO_LE; */
/*         SWAP(int, topLimit, btmLimit); */
/*       } */

/*       /1* Generate the termination key.  This is the key value that */
/*       ** will end the search.  There is no termination key if there */
/*       ** are no equality terms and no "X<..." term. */
/*       ** */
/*       ** 2002-Dec-04: On a reverse-order scan, the so-called "termination" */
/*       ** key computed here really ends up being the start key. */
/*       *1/ */
/*       if( topLimit ){ */
/*         Expr *pX; */
/*         int k = pIdx->aiColumn[j]; */
/*         pTerm = findTerm(&wc, iCur, k, notReady, topOp, pIdx); */
/*         assert( pTerm!=0 ); */
/*         pX = pTerm->pExpr; */
/*         assert( (pTerm->flags & TERM_CODED)==0 ); */
/*         sqlite3ExprCode(pParse, pX->pRight); */
/*         topEq = pTerm->eOperator & (WO_LE|WO_GE); */
/*         disableTerm(pLevel, pTerm); */
/*         testOp = OP_IdxGE; */
/*       }else{ */
/*         testOp = nEq>0 ? OP_IdxGE : OP_Noop; */
/*         topEq = 1; */
/*       } */
/*       if( testOp!=OP_Noop ){ */
/*         int nCol = nEq + topLimit; */
/*         pLevel->iMem = pParse->nMem++; */
/*         buildIndexProbe(v, nCol, nEq, brk, pIdx); */
/*         if( bRev ){ */
/*           int op = topEq ? OP_MoveLe : OP_MoveLt; */
/*           sqlite3VdbeAddOp(v, op, iIdxCur, brk); */
/*         }else{ */
/*           sqlite3VdbeAddOp(v, OP_MemStore, pLevel->iMem, 1); */
/*         } */
/*       }else if( bRev ){ */
/*         sqlite3VdbeAddOp(v, OP_Last, iIdxCur, brk); */
/*       } */

/*       /1* Generate the start key.  This is the key that defines the lower */
/*       ** bound on the search.  There is no start key if there are no */
/*       ** equality terms and if there is no "X>..." term.  In */
/*       ** that case, generate a "Rewind" instruction in place of the */
/*       ** start key search. */
/*       ** */
/*       ** 2002-Dec-04: In the case of a reverse-order search, the so-called */
/*       ** "start" key really ends up being used as the termination key. */
/*       *1/ */
/*       if( btmLimit ){ */
/*         Expr *pX; */
/*         int k = pIdx->aiColumn[j]; */
/*         pTerm = findTerm(&wc, iCur, k, notReady, btmOp, pIdx); */
/*         assert( pTerm!=0 ); */
/*         pX = pTerm->pExpr; */
/*         assert( (pTerm->flags & TERM_CODED)==0 ); */
/*         sqlite3ExprCode(pParse, pX->pRight); */
/*         btmEq = pTerm->eOperator & (WO_LE|WO_GE); */
/*         disableTerm(pLevel, pTerm); */
/*       }else{ */
/*         btmEq = 1; */
/*       } */
/*       if( nEq>0 || btmLimit ){ */
/*         int nCol = nEq + btmLimit; */
/*         buildIndexProbe(v, nCol, 0, brk, pIdx); */
/*         if( bRev ){ */
/*           pLevel->iMem = pParse->nMem++; */
/*           sqlite3VdbeAddOp(v, OP_MemStore, pLevel->iMem, 1); */
/*           testOp = OP_IdxLT; */
/*         }else{ */
/*           int op = btmEq ? OP_MoveGe : OP_MoveGt; */
/*           sqlite3VdbeAddOp(v, op, iIdxCur, brk); */
/*         } */
/*       }else if( bRev ){ */
/*         testOp = OP_Noop; */
/*       }else{ */
/*         sqlite3VdbeAddOp(v, OP_Rewind, iIdxCur, brk); */
/*       } */

/*       /1* Generate the the top of the loop.  If there is a termination */
/*       ** key we have to test for that key and abort at the top of the */
/*       ** loop. */
/*       *1/ */
/*       start = sqlite3VdbeCurrentAddr(v); */
/*       if( testOp!=OP_Noop ){ */
/*         sqlite3VdbeAddOp(v, OP_MemLoad, pLevel->iMem, 0); */
/*         sqlite3VdbeAddOp(v, testOp, iIdxCur, brk); */
/*         if( (topEq && !bRev) || (!btmEq && bRev) ){ */
/*           sqlite3VdbeChangeP3(v, -1, "+", P3_STATIC); */
/*         } */
/*       } */
/*       sqlite3VdbeAddOp(v, OP_RowKey, iIdxCur, 0); */
/*       sqlite3VdbeAddOp(v, OP_IdxIsNull, nNotNull, cont); */
/*       if( !omitTable ){ */
/*         sqlite3VdbeAddOp(v, OP_IdxRowid, iIdxCur, 0); */
/*         sqlite3VdbeAddOp(v, OP_MoveGe, iCur, 0); */
/*       } */

/*       /1* Record the instruction used to terminate the loop. */
/*       *1/ */
/*       pLevel->op = bRev ? OP_Prev : OP_Next; */
/*       pLevel->p1 = iIdxCur; */
/*       pLevel->p2 = start; */
/*     }else if( pLevel->flags & WHERE_COLUMN_EQ ){ */
/*       /1* Case 4:  There is an index and all terms of the WHERE clause that */
/*       **          refer to the index using the "==" or "IN" operators. */
/*       *1/ */
/*       int start; */
/*       int nEq = pLevel->nEq; */

/*       /1* Generate code to evaluate all constraint terms using == or IN */
/*       ** and leave the values of those terms on the stack. */
/*       *1/ */
/*       codeAllEqualityTerms(pParse, pLevel, &wc, notReady, brk); */

/*       /1* Generate a single key that will be used to both start and terminate */
/*       ** the search */
/*       *1/ */
/*       buildIndexProbe(v, nEq, 0, brk, pIdx); */
/*       sqlite3VdbeAddOp(v, OP_MemStore, pLevel->iMem, 0); */

/*       /1* Generate code (1) to move to the first matching element of the table. */
/*       ** Then generate code (2) that jumps to "brk" after the cursor is past */
/*       ** the last matching element of the table.  The code (1) is executed */
/*       ** once to initialize the search, the code (2) is executed before each */
/*       ** iteration of the scan to see if the scan has finished. *1/ */
/*       if( bRev ){ */
/*         /1* Scan in reverse order *1/ */
/*         sqlite3VdbeAddOp(v, OP_MoveLe, iIdxCur, brk); */
/*         start = sqlite3VdbeAddOp(v, OP_MemLoad, pLevel->iMem, 0); */
/*         sqlite3VdbeAddOp(v, OP_IdxLT, iIdxCur, brk); */
/*         pLevel->op = OP_Prev; */
/*       }else{ */
/*         /1* Scan in the forward order *1/ */
/*         sqlite3VdbeAddOp(v, OP_MoveGe, iIdxCur, brk); */
/*         start = sqlite3VdbeAddOp(v, OP_MemLoad, pLevel->iMem, 0); */
/*         sqlite3VdbeOp3(v, OP_IdxGE, iIdxCur, brk, "+", P3_STATIC); */
/*         pLevel->op = OP_Next; */
/*       } */
/*       sqlite3VdbeAddOp(v, OP_RowKey, iIdxCur, 0); */
/*       sqlite3VdbeAddOp(v, OP_IdxIsNull, nEq, cont); */
/*       if( !omitTable ){ */
/*         sqlite3VdbeAddOp(v, OP_IdxRowid, iIdxCur, 0); */
/*         sqlite3VdbeAddOp(v, OP_MoveGe, iCur, 0); */
/*       } */
/*       pLevel->p1 = iIdxCur; */
/*       pLevel->p2 = start; */
/*     }else{ */
/*       /1* Case 5:  There is no usable index.  We must do a complete */
/*       **          scan of the entire table. */
/*       *1/ */
/*       assert( omitTable==0 ); */
/*       assert( bRev==0 ); */
/*       pLevel->op = OP_Next; */
/*       pLevel->p1 = iCur; */
/*       pLevel->p2 = 1 + sqlite3VdbeAddOp(v, OP_Rewind, iCur, brk); */
/*     } */
/*     notReady &= ~getMask(&maskSet, iCur); */

/*     /1* Insert code to test every subexpression that can be completely */
/*     ** computed using the current set of tables. */
/*     *1/ */
/*     for(pTerm=wc.a, j=wc.nTerm; j>0; j--, pTerm++){ */
/*       Expr *pE; */
/*       if( pTerm->flags & (TERM_VIRTUAL|TERM_CODED) ) continue; */
/*       if( (pTerm->prereqAll & notReady)!=0 ) continue; */
/*       pE = pTerm->pExpr; */
/*       assert( pE!=0 ); */
/*       if( pLevel->iLeftJoin && !ExprHasProperty(pE, EP_FromJoin) ){ */
/*         continue; */
/*       } */
/*       sqlite3ExprIfFalse(pParse, pE, cont, 1); */
/*       pTerm->flags |= TERM_CODED; */
/*     } */

/*     /1* For a LEFT OUTER JOIN, generate code that will record the fact that */
/*     ** at least one row of the right table has matched the left table. */
/*     *1/ */
/*     if( pLevel->iLeftJoin ){ */
/*       pLevel->top = sqlite3VdbeCurrentAddr(v); */
/*       sqlite3VdbeAddOp(v, OP_MemInt, 1, pLevel->iLeftJoin); */
/*       VdbeComment((v, "# record LEFT JOIN hit")); */
/*       for(pTerm=wc.a, j=0; j<wc.nTerm; j++, pTerm++){ */
/*         if( pTerm->flags & (TERM_VIRTUAL|TERM_CODED) ) continue; */
/*         if( (pTerm->prereqAll & notReady)!=0 ) continue; */
/*         assert( pTerm->pExpr ); */
/*         sqlite3ExprIfFalse(pParse, pTerm->pExpr, cont, 1); */
/*         pTerm->flags |= TERM_CODED; */
/*       } */
/*     } */
/*   } */

/* #ifdef SQLITE_TEST  /1* For testing and debugging use only *1/ */
/*   /1* Record in the query plan information about the current table */
/*   ** and the index used to access it (if any).  If the table itself */
/*   ** is not used, its name is just '{}'.  If no index is used */
/*   ** the index is listed as "{}".  If the primary key is used the */
/*   ** index name is '*'. */
/*   *1/ */
/*   for(i=0; i<pTabList->nSrc; i++){ */
/*     char *z; */
/*     int n; */
/*     pLevel = &pWInfo->a[i]; */
/*     pTabItem = &pTabList->a[pLevel->iFrom]; */
/*     z = pTabItem->zAlias; */
/*     if( z==0 ) z = pTabItem->pTab->zName; */
/*     n = strlen(z); */
/*     if( n+nQPlan < sizeof(sqlite3_query_plan)-10 ){ */
/*       if( pLevel->flags & WHERE_IDX_ONLY ){ */
/*         strcpy(&sqlite3_query_plan[nQPlan], "{}"); */
/*         nQPlan += 2; */
/*       }else{ */
/*         strcpy(&sqlite3_query_plan[nQPlan], z); */
/*         nQPlan += n; */
/*       } */
/*       sqlite3_query_plan[nQPlan++] = ' '; */
/*     } */
/*     if( pLevel->flags & (WHERE_ROWID_EQ|WHERE_ROWID_RANGE) ){ */
/*       strcpy(&sqlite3_query_plan[nQPlan], "* "); */
/*       nQPlan += 2; */
/*     }else if( pLevel->pIdx==0 ){ */
/*       strcpy(&sqlite3_query_plan[nQPlan], "{} "); */
/*       nQPlan += 3; */
/*     }else{ */
/*       n = strlen(pLevel->pIdx->zName); */
/*       if( n+nQPlan < sizeof(sqlite3_query_plan)-2 ){ */
/*         strcpy(&sqlite3_query_plan[nQPlan], pLevel->pIdx->zName); */
/*         nQPlan += n; */
/*         sqlite3_query_plan[nQPlan++] = ' '; */
/*       } */
/*     } */
/*   } */
/*   while( nQPlan>0 && sqlite3_query_plan[nQPlan-1]==' ' ){ */
/*     sqlite3_query_plan[--nQPlan] = 0; */
/*   } */
/*   sqlite3_query_plan[nQPlan] = 0; */
/*   nQPlan = 0; */
/* #endif /1* SQLITE_TEST // Testing and debugging use only *1/ */

/*   /1* Record the continuation address in the WhereInfo structure.  Then */
/*   ** clean up and return. */
/*   *1/ */
/*   pWInfo->iContinue = cont; */
/*   whereClauseClear(&wc); */
/*   return pWInfo; */

/*   /1* Jump here if malloc fails *1/ */
/* whereBeginNoMem: */
/*   whereClauseClear(&wc); */
/*   sqliteFree(pWInfo); */
/*   return 0; */
/* } */

/*
** Generate the end of the WHERE loop.  See comments on
** sqlite3WhereBegin() for additional information.
*/
/* void sqlite3WhereEnd(WhereInfo *pWInfo){ */
/*   Vdbe *v = pWInfo->pParse->pVdbe; */
/*   int i; */
/*   WhereLevel *pLevel; */
/*   SrcList *pTabList = pWInfo->pTabList; */

/*   /1* Generate loop termination code. */
/*   *1/ */
/*   for(i=pTabList->nSrc-1; i>=0; i--){ */
/*     pLevel = &pWInfo->a[i]; */
/*     sqlite3VdbeResolveLabel(v, pLevel->cont); */
/*     if( pLevel->op!=OP_Noop ){ */
/*       sqlite3VdbeAddOp(v, pLevel->op, pLevel->p1, pLevel->p2); */
/*     } */
/*     sqlite3VdbeResolveLabel(v, pLevel->brk); */
/*     if( pLevel->nIn ){ */
/*       int *a; */
/*       int j; */
/*       for(j=pLevel->nIn, a=&pLevel->aInLoop[j*3-3]; j>0; j--, a-=3){ */
/*         sqlite3VdbeAddOp(v, a[0], a[1], a[2]); */
/*       } */
/*       sqliteFree(pLevel->aInLoop); */
/*     } */
/*     if( pLevel->iLeftJoin ){ */
/*       int addr; */
/*       addr = sqlite3VdbeAddOp(v, OP_IfMemPos, pLevel->iLeftJoin, 0); */
/*       sqlite3VdbeAddOp(v, OP_NullRow, pTabList->a[i].iCursor, 0); */
/*       if( pLevel->iIdxCur>=0 ){ */
/*         sqlite3VdbeAddOp(v, OP_NullRow, pLevel->iIdxCur, 0); */
/*       } */
/*       sqlite3VdbeAddOp(v, OP_Goto, 0, pLevel->top); */
/*       sqlite3VdbeJumpHere(v, addr); */
/*     } */
/*   } */

/*   /1* The "break" point is here, just past the end of the outer loop. */
/*   ** Set it. */
/*   *1/ */
/*   sqlite3VdbeResolveLabel(v, pWInfo->iBreak); */

/*   /1* Close all of the cursors that were opened by sqlite3WhereBegin. */
/*   *1/ */
/*   for(i=0, pLevel=pWInfo->a; i<pTabList->nSrc; i++, pLevel++){ */
/*     struct SrcList_item *pTabItem = &pTabList->a[pLevel->iFrom]; */
/*     Table *pTab = pTabItem->pTab; */
/*     assert( pTab!=0 ); */
/*     if( pTab->isTransient || pTab->pSelect ) continue; */
/*     if( (pLevel->flags & WHERE_IDX_ONLY)==0 ){ */
/*       sqlite3VdbeAddOp(v, OP_Close, pTabItem->iCursor, 0); */
/*     } */
/*     if( pLevel->pIdx!=0 ){ */
/*       sqlite3VdbeAddOp(v, OP_Close, pLevel->iIdxCur, 0); */
/*     } */

/*     /1* Make cursor substitutions for cases where we want to use */
/*     ** just the index and never reference the table. */
/*     ** */
/*     ** Calls to the code generator in between sqlite3WhereBegin and */
/*     ** sqlite3WhereEnd will have created code that references the table */
/*     ** directly.  This loop scans all that code looking for opcodes */
/*     ** that reference the table and converts them into opcodes that */
/*     ** reference the index. */
/*     *1/ */
/*     if( pLevel->flags & WHERE_IDX_ONLY ){ */
/*       int k, j, last; */
/*       VdbeOp *pOp; */
/*       Index *pIdx = pLevel->pIdx; */

/*       assert( pIdx!=0 ); */
/*       pOp = sqlite3VdbeGetOp(v, pWInfo->iTop); */
/*       last = sqlite3VdbeCurrentAddr(v); */
/*       for(k=pWInfo->iTop; k<last; k++, pOp++){ */
/*         if( pOp->p1!=pLevel->iTabCur ) continue; */
/*         if( pOp->opcode==OP_Column ){ */
/*           pOp->p1 = pLevel->iIdxCur; */
/*           for(j=0; j<pIdx->nColumn; j++){ */
/*             if( pOp->p2==pIdx->aiColumn[j] ){ */
/*               pOp->p2 = j; */
/*               break; */
/*             } */
/*           } */
/*         }else if( pOp->opcode==OP_Rowid ){ */
/*           pOp->p1 = pLevel->iIdxCur; */
/*           pOp->opcode = OP_IdxRowid; */
/*         }else if( pOp->opcode==OP_NullRow ){ */
/*           pOp->opcode = OP_Noop; */
/*         } */
/*       } */
/*     } */
/*   } */

/*   /1* Final cleanup */
/*   *1/ */
/*   sqliteFree(pWInfo); */
/*   return; */
/* } */
